The present application is based on Japanese Patent Application No. 2001-170911, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a Group III nitride compound semiconductor light-emitting element. It is adapted for improvement in electrodes of a Group III nitride compound semiconductor light-emitting element such as a blue light-emitting diode.
2. Description of the Related Art
Various proposals have been made for obtaining uniform light emission from the whole surface of a Group III nitride compound semiconductor light-emitting element such as a blue light-emitting diode.
As a measure to obtain uniform light emission, there is a method in which a p seat electrode is provided on a thin-film light-transmissive electrode stuck onto an upper surface of a p-type layer (Unexamined Japanese Patent Publication No. Hei. 10-275934).
The light-transmissive electrode and the p seat electrode are formed as follows.
First, a material layer for forming a light-transmissive electrode is formed on a p-type layer, for example, by a lift-off method. Then, the material layer for forming a light-transmissive electrode is ashed according to an ordinary method, and a material layer for forming a p seat electrode is likewise formed by a lift-off method.
Then, the two layers are heated to be alloyed with and bonded to each other.
According to the prevent inventor"" examination, it has been found occasionally that gas is generated between a material for forming a light-transmissive electrode and a material for forming a p seat electrode when the two materials are heated to be alloyed with each other. There has been a fear that sufficient adhesion or ohmic contact cannot be obtained between the p seat electrode and the light-transmissive electrode because the p seat electrode is swollen by the gas after alloying.
According to a trial to find the cause of generation of the gas, it has been found that gas is generated because so-called contaminant (organic matter, resist residue, etc.) deposited on a surface of the material for forming the light-transmissive electrode is decomposed by the temperature on the basis of heating for alloying.
It may be conceived that strict control over the ashing condition or the like can prevent the contaminant from being deposited on the surface. It is, however, actually difficult to remove the contaminant thoroughly because the step condition (the state of an apparatus, the environmental factor in a clean room, the characteristic of each semiconductor layer, etc.) fluctuates.
The invention is the fruit of the inventor""s eager examination for solving the problem. That is, the invention is configured as follows.
A method of producing a Group III nitride compound semiconductor light-emitting element, including the steps of:
laminating a p seat electrode on a light-transmissive electrode;
removing gas (degassing) from between the light-transmissive electrode and the p seat electrode; and
alloying the light-transmissive electrode and the p seat electrode with each other after the degassing step is carried out.
According to the producing method of the invention, the p seat electrode is prevented from being swollen because gas is removed from between the light-transmissive electrode and the p seat electrode before the two electrodes are alloyed with each other. Hence, sufficient adhesion is obtained between the light-transmissive electrode and the p seat electrode as well as ohmic characteristic is secured between the two electrodes.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.